Are eels climbing back up the slippery slope?

The issue of dwindling numbers of Anguilla eel has featured highly on the agenda of many aquatic biologists and researchers, but as a recent ICES-sponsored symposium in Quebec sought to ask, are they climbing back up the slippery slope?

Published:
4 September 2014

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Historically, the going has been particularly tough for the cosmopolitan genus Anguilla, which includes the European and American eel. These creatures occupy estuarine, coastal, and freshwater habitats in many regions around the world but spawn in the open ocean. For the likes of the European eel, swinging between these two habitats entails a treacherous migration across the Atlantic Ocean; for all species, moving from continental to oceanic water presents a challenge, with a raft of obstacles and often fishers lying in wait.

Factors such as habitat loss caused by dams, mortality from hydropower turbines, fisheries, changes in ocean conditions, chemical contamination, and the introduction of alien species have combined to land many, if not most, Anguilla eel species in conservation difficulty. Added to this is the fact that, although most eels sold on the world market are now farm-reared, aquaculture has increased pressure on a growing number of wild stocks, because aquaculture seedstock comes from wild eels harvested at the glass eel or elver stage.

Declaration of concern

In 2003, the annual meeting of the American Fisheries Society hosted an international eel symposium, also in Quebec City, which proved to be a pivotal moment in eel conservation history. The "Quebec Declaration of Concern," produced at that session and published in the AFS Fisheries magazine, mobilized scientific research and monitoring of eels worldwide and, to varying degrees, spurred improved management efforts.

Marking progress

Over a decade later, the same French-Canadian city has seen the subject reprised in the shape of the International Eel Symposium 2014. Held as part of the annual meeting of the American Fisheries Society, 18-21 August, experts in the field met to determine whether worldwide eel populations are beginning to re-climb the slippery slope of past declines. Have the measures set out 11 years ago provided adequate protection? What indeed is adequate? In seeing to these questions and getting to grips with the core issues surrounding populations of these creatures, the conference aimed to chart progress made since 2003.

A forum for all things eel

A suite of presentations – both oral and poster – was made during the symposium, with key themes in eel biology and management being explored – including remarkable advances in eel genetics and the history of human interaction with European eels, from the Doomsday Book of medieval England to the current multinational management system mandated by the European Union and supported by ICES science and advice.

One talk put the current status of captive eel breeding under the spotlight, looking at efforts to improve its cost efficiency to the point where it can replace wild harvest as seedstock for the aquaculture industry. Other covered topics advances in assessment methods, impacts of introduced parasites, and socio-economics of eel fisheries. There was also a rich contribution of papers on the effects of dams on eels, which examined impacts on habitat access and turbine mortality whilst analysing relevant mitigative options.

European plan a model case

Rounding off the symposium was a Round Table discussion chaired by Bob Lambe of the Great Lakes Fisheries Commission and involving panellists from Canada, Germany, the US, and the UK. The specialists emphasized the fragile nature of recent upswings in eel recruitment as well as the difficulty in attributing human and natural influences to these shifts. Discussion also centred on the need to manage panmictic (the random mating of a population’s individuals) eel stocks through inter-jurisdictional management and the need to communicate eel conservation issues to a wide audience. The European eel is currently the only eel species with an international management regime, and is seen as providing a model for other species, whose management is at best regional or national, or in some cases, entirely absent.

The group also noted that ICES is a potential forum for international assessment of the American eel, given its heritage in eel science, its Canadian and US membership, and the precedent of a previous ICES American eel evaluation in 2000.

Climbing up the slippery slope?

Following the Round Table meeting, a small group assembled to draft a document to be titled 'The 2003 Quebec Declaration of Concern - 11 Years After: Are Eels Climbing Back up the Slippery Slope?'

Whilst the document will be circulated for endorsement, the question it poses, and the one institutionalized in the official symposium title, speaks of an existential plight corroborated by science and research and one that catalyzed global experts to take action.

But how far has the species come in just over a decade? Well, with a modest reversal in recruitment fortunes and the appropriate management mechanisms in place, the species may be on the right track, but the slope is indeed long, and the science delivered and deliberated over at the symposium represents only the first, tentative footsteps back up it. However, it is hoped that, as the initial 2003 meeting drew attention to the troubles facing these ancient animals, the 2014 event will be remembered as the point at which the tide began to turn.